[media] cx231xx: register i2c mux adapters for bus 1

I2C bus 1 has internally a switch. Use it as I2C_1_MUX_1 and
I2C_1_MUX_3, letting the I2C core handling the switch.

Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>